Peer to peer ranging exchange

Abstract

A method for discovering devices in a peer to peer (P2P) wireless communication network is described. During a search state of a first communication device, a probe request is transmitted by the first communication device on a first channel included in a plurality of channels. During the search state, a probe response transmitted by a second communication device on the first channel is received by the first communication device. In response to the probe response, a ranging exchange with the second communication device is performed by the first communication device.

What is claimed is: 
     
       1. A method for discovering devices in a peer to peer (P2P) wireless communication network, the method comprising:
 during a search state of a first communication device, transmitting, by the first communication device, a first probe request on a first channel included in a plurality of channels, wherein the search state (i) is one of a plurality of different states in which the first communication device is configured to operate, and (ii) corresponds to a contiguous time period in which the first communication device is configured to transmit multiple probe requests on different channels among the plurality of channels; 
 during the search state, receiving, by the first communication device, a first probe response transmitted by a second communication device on the first channel; 
 in response to receiving the first probe response, performing, by the first communication device, a ranging exchange with the second communication device; 
 during an advertise state of the first communication device, listening, by the first communication device, for probe requests on a second channel included in the plurality of channels, wherein the advertise state corresponds to another contiguous time period in which the first communication device is configured to listen for probe requests on a single channel, and wherein a duration of the other contiguous time period is randomly or pseudo-randomly determined by the first communication device; 
 during the advertise state, transmitting, by the first communication device, a second probe response to a second probe request transmitted by a third communication device on the second channel if the second probe request is received on the second channel during the advertise state; 
 during the advertise state and in response to the second probe request, listening, by the first communication device, for probe requests on the second channel and for a ranging request transmitted by the third communication device; and 
 during the advertise state and in response to the ranging request 
 transmitting, by the first communication device, a first action frame having a dialog token for a fine timing measurement exchange, and 
 storing, by the first communication device, a first departure time indicator for the first action frame. 
 
     
     
       2. The method of  claim 1 , wherein the first communication device performs the ranging exchange without first joining a P2P group with the second communication device. 
     
     
       3. The method of  claim 1 , wherein performing the ranging exchange comprises performing the ranging exchange during the search state of the first communication device on the first channel. 
     
     
       4. The method of  claim 3 , further comprising maintaining, by the first communication device, the search state of the first communication device on the first channel until an end of the ranging exchange. 
     
     
       5. The method of  claim 1 , further comprising:
 determining, by the first communication device, whether the second communication device is within a threshold range based on the ranging exchange; and 
 in response to a determination that the second communication device is within the threshold range, performing, by the first communication device, a group formation procedure to form a P2P group with the second communication device. 
 
     
     
       6. The method of  claim 5 , wherein performing the ranging exchange comprises:
 transmitting, by the first communication device, a ranging request to the second communication device; 
 storing, by the first communication device, a first arrival time indicator that corresponds to a second action frame transmitted by the second communication device in response to the ranging request transmitted by the first communication device; 
 transmitting, by the first communication device, an acknowledgment to the second action frame; 
 storing, by the first communication device, a second departure time indicator for the acknowledgement to the second action frame; and 
 in response to a third action frame transmitted by the second communication device, estimating, by the first communication device, a round trip time between the first communication device and the second communication device based on i) the first arrival time indicator, ii) a third departure time indicator that corresponds to the second action frame, iii) a second arrival time indicator that corresponds to the acknowledgment to the second action frame, and iv) the second departure time indicator, the third action frame including the third departure time indicator and the second arrival time indicator. 
 
     
     
       7. The method of  claim 6 , wherein:
 the first arrival time indicator has a value T2, the third departure time indicator has a value T1, the second arrival time indicator has a value T4, and the second departure time indicator has a value T3, and 
 estimating the round trip time comprises determining the round trip time as:
   ( T 4− T 1)−( T 3− T 2).
 
 
 
     
     
       8. The method of  claim 6 , wherein performing the ranging exchange comprises setting a reference time for the ranging exchange based on a timing synchronization function value that corresponds to the first probe response. 
     
     
       9. The method of  claim 1 , further comprising:
 during the advertise state and in response to an acknowledgment to the first action frame transmitted by the third communication device, transmitting, by the first communication device, a second action frame that indicates the first departure time indicator for the first action frame and an arrival time indicator of the acknowledgment of the first action frame. 
 
     
     
       10. The method of  claim 1 , wherein:
 the ranging request includes one or more timing parameters for the ranging exchange; and 
 transmitting the first action frame comprises: 
 modifying at least one of the one or more timing parameters to avoid absence periods of the first communication device, and 
 transmitting the first action frame using the one or more timing parameters including the at least one modified timing parameter. 
 
     
     
       11. The method of  claim 10 , wherein modifying the at least one of the one or more timing parameters comprises modifying a start time of the one or more timing parameters to avoid the absence periods. 
     
     
       12. The method of  claim 10 , wherein modifying the at least one of the one or more timing parameters comprises modifying an action frame interval of the one or more timing parameters to avoid the absence periods. 
     
     
       13. A first communication device, comprising:
 a network interface device configured to:
 during a search state of a first communication device, transmit a first probe request on a first channel included in a plurality of channels, wherein the search state (i) is one of a plurality of different states in which the first communication device is configured to operate, and (ii) corresponds to a contiguous time period in which the first communication device is configured to transmit multiple probe requests on different channels among the plurality of channels, 
 during the search state, receive a first probe response transmitted by a second communication device on the first channel, 
 in response to the received first probe response, perform a ranging exchange with the second communication device, 
 during an advertise state of the first communication device, listen for probe requests on a second channel included in the plurality of channels, wherein the advertise state corresponds to another contiguous time period in which the first communication device is configured to listen for probe requests on a single channel, and wherein a duration of the other contiguous time period is randomly or pseudo-randomly determined by the first communication device, 
 during the advertise state, transmit a second probe response to a second probe request transmitted by a third communication device on the second channel if the second probe request is received on the second channel during the advertise state, 
 during the advertise state and in response to the second probe request, listen for probe requests on the second channel and for a ranging request transmitted by the third communication device, and 
 during the advertise state and in response to the ranging request 
 i) transmit a first action frame having a dialog token for a fine timing measurement exchange, and 
 ii) store a first departure time indicator for the first action frame. 
 
 
     
     
       14. The first communication device of  claim 13 , wherein the network interface device is configured to:
 perform the ranging exchange without first joining a peer-to-peer group with the second communication device. 
 
     
     
       15. The first communication device of  claim 13 , wherein the network interface device is configured to:
 perform the ranging exchange during the search state of the first communication device on the first channel. 
 
     
     
       16. The first communication device of  claim 15 , wherein the network interface device is further configured to:
 maintain the search state of the first communication device on the first channel until an end of the ranging exchange. 
 
     
     
       17. The first communication device of  claim 13 , wherein the network interface device is further configured to:
 determine whether the second communication device is within a threshold range based on the ranging exchange; and 
 in response to a determination that the second communication device is within the threshold range, perform a group formation procedure to form a peer-to-peer (P2P) group with the second communication device. 
 
     
     
       18. The first communication device of  claim 13 , wherein the network interface device is further configured to:
 during the advertise state and in response to an acknowledgment to the first action frame transmitted by the third communication device, transmit a second action frame that indicates the first departure time indicator for the first action frame and an arrival time indicator of the acknowledgment of the first action frame. 
 
     
     
       19. The first communication device of  claim 13 , wherein:
 the ranging request includes one or more timing parameters for the ranging exchange; and 
 the network interface device is configured to 
 modify at least one of the one or more timing parameters to avoid absence periods of the first communication device, and 
 transmit the first action frame using the one or more timing parameters including the at least one modified timing parameter. 
 
     
     
       20. The first communication device of  claim 19 , wherein the network interface device is configured to modify a start time of the one or more timing parameters to avoid the absence periods. 
     
     
       21. The first communication device of  claim 19 , wherein the network interface device is configured to modify an action frame interval of the one or more timing parameters to avoid the absence periods.